The invention relates to a radio transmission and reception apparatus having a PLL circuit for modulation and demodulation, respectively.
Radio transmission and reception apparatuses in which the transmitting section and the receiving section are each equipped with a PLL circuit for signal modulation and demodulation or in which only the receiving section or the transmitting section has a PLL circuit are state of the art and are known from, for example, R. Best, "Theorie und Anwendung des Phase-locked Loops" [Theory and Application of the Phase Locked Loop], published by AT-Verlag, 1987, in particular pages 87-91. In the circuit arrays first mentioned, the high component requirement and hence the high manufacturing costs can be cited as a drawback. In the last-mentioned circuits, the advantages of PLL-controlled modulations or demodulations are dispensed with in either the transmitting section or the receiving section.
The object of the invention is therefore to provide a radio transmission and reception apparatus permitting the use of a PLL circuit in both the transmitting and receiving sections of the apparatus, with fewer components and a lower space requirement. The above object is achieved according to the present invention by a radio transmission and reception apparatus having a transmitting section and a receiving section, and wherein the transmitting and receiving sections have a common PLL circuit for signal modulation and demodulation, respectively. Preferably, the common PLL circuit comprises a phase detector, a first VCO and a further oscillator operating either as a reference oscillator or as a second VCO. A switch arrangement is provided such that in the transmitting state of the radio transmission and reception apparatus, the feedback loop of the PLL circuit is closed via the first VCO and the further oscillator operates as a reference oscillator, and, in the receiving state of the radio transmission and reception apparatus, the feedback loop is closed via the further oscillator operating now as a VCO (the first VCO being disabled) and the phase detector is connected to the output of an HF input stage.
One major advantage of the invention is that in a combined radio transmission and reception apparatus in accordance with the invention, a large proportion of the components of the phase-locked loop is used both for signal modulation during transmission as well as for signal demodulation during reception. This joint use of a circuit component for both the transmitting section and the receiving section can be used to particular advantage above all in radio transmission and reception apparatuses in which data transmission is bidirectional in the time-division multiplex mode. Performance of the transmission and reception tasks is not simultaneous, but alternating in time. The radio transmission and reception apparatus can be set to a transmitting or receiving state using simple switching methods. Various advantageous embodiments of the invention are likewise disclosed.